Military suspends flight of Surion choppers over defective gearbox


Published : 2016-07-07 11:43
Updated : 2016-07-07 11:43

Korea’s military has suspended the flight of locally-developed KUH-1 Surion helicopter after defects in the imported gearbox were reported following the deadly crash of a Norwegian chopper using the same European component, the defense procurement agency said Thursday.

The EC-225 Super Puma chopper of Norwegian oil company Statoil crashed off the Scandinavian country’s southwest coast on April 29, killing all 13 people aboard.

Korea has recently been informed by the chopper’s manufacturer, Airbus Helicopters, that the crash was due to the defective main gearbox that connects the aircraft’s engine with the rotor system.

“Some of Surion choppers are equipped with the same main gearbox, so the flight of these aircraft has been put on hold to prevent potential accidents,” an official at the Defense Acquisition Program Administration  said.

The multi-role Surion chopper was produced by Korea’s sole aircraft manufacturer Korea Aerospace Industries Ltd. as part of a 1.3 trillion won military procurement project. About 57 percent of the military-use Surion choppers are equipped with the gearbox made by Airbus Helicopters.

Since its first flight test in 2010, the indigenous aircraft has been adapted for military purposes as well as other non-military missions for the police and the firefighters.

With financial reimbursement from Airbus Helicopters, the DAPA plans to replace the defective components by the end of this year, the official said. (Yonhap)


EC225 Main Rotor Head and Main Gear Box Design

EC225/H225 Main Rotor Head and Main Gear Box Design

Following the recent tragic accident at Turøy near Bergen, Norway involving EC225/H225 LN-OJF there is a lot of interest in the Main Rotor (MR) and Main Gear Box (MGB) design of the EC225.  Here we provide some background information on the design and updates on the investigation and regulatory action.

The EC225/H225 MRH/MGB Design


EC225 MRH and MGB (c) Aerossurance

Unlike some other types, the 11t+ lift load from the Main Rotor is not imposed on the casing of the MGB, but is instead transferred via a Double Taper Bearing to the Lift Housing (see the diagram below).  When static the Double Taper Bearing also transmits the weight of the MR assembly to the Lift Housing.

The Lift Housing is connected to the fuselage via three Suspension Bars (which connect to fittings secured to the fuselage by 4 bolts).  The Lift Housing also takes the suspended weight of the MGB via the Flared Housing.  The MGB is supported underneath by the flexible titanium Barbeque Plate which absorbs the MR torque, longitudinal and transverse loads and damps out vibrations.


EC225 MRH and MGB (Credit: Airbus Helicopters via Aerobuzz with Aerossurance Labelling)

The EC225 has a integral Main Rotor Head (MRH) and MR shaft, which mates with output of the MGB Epicyclic Module via a spline.  The five Blade Sleeves (and their associated Blade Dampers) are attached to the MRH.  The composite Main Rotor Blades (MRBs) are fitted to the Blade Sleeves.

As is conventional on a helicopter, the pitch of the MRBs is controlled by Pitch Change Rods connecting the Rotating Swashplate to the Blade Sleeves.  The Rotating Swashplate follows the position of the Non-Rotating Swashplate, which is moved by three flying control Servo Units (not shown above), in responses to movement of the pilot’s Cyclic and Collective Controls.  The Rotating Swashplate oscillates around a ball joint which can also slide up and down a Guide Tube that surrounds the MR Shaft.  Each part of the Swashplate has a two part articulating Scissor.  The one connected to the MRH drives the Rotating Swashplate, while the one connected to the Lift Housing prevents the Non-Rotating Swashplate from rotating.

The MGB is modular, with a main module which drives an epicyclic module and two accessory modules.  Drive from the two 2101 shp Turbomeca Makila 2A engines enters the front of the MGB via two high speed (22962 rpm) shafts (known as Bendix shafts). The MGB Main Module and the 2 stage Epicyclic Module reduce the speed to the nominal Main Rotor speed of 265 rpm.  The Main Module also drives various accessories and the Tail Rotor Drive Shaft (TRDS).


EC225/H225 MGB Schematic (Credit: Airbus Helicopters via Step Change in Safety)


Close Up on EC225/H225 MGB Main Module and Epicyclic Module (Credit: Airbus Helicopters via AIBN)

The LN-OJF Investigation

The independent Accident Investigation Board Norway (AIBN – the Statens Havarikommisjon for Transport [SHT] in Norwegian) is leading the LN-OJF accident investigation in accordance with the International Civil Aviation Organisation (ICAO) Annex 13 on air accident investigation.

The AIBN have issued the following press releases:

Read entire article: Here

Related news:

Norway helicopter crash: Airbus grounds Super Puma after 13 presumed killed – ABC

KAI KUH-1 Surion: Details


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